Study on Direct Contact Heat Transfer during MEB in Subcooled Pool Boiling

Abstract

Microbubble Emission Boiling, so-called MEB, shows a different boiling curve in the transition boiling region under subcooled boiling conditions. It is characterized by an increase in heat flux even beyond the critical heat flux (CHF). Many studies on MEB have been carried out in recent years, but the mechanism of occurrence and the heat transfer characteristics are still unknown. In this study, we experimentally consider the heat transfer mechanism from bubble behavior by measuring the cycle of direct contact of subcooled water to the heat transfer surface using boiling sound and high-speed video images. In addition, the relation between the dry-out area on the heat transfer surface and the heat flux was examined based on the microlayer model. Especially, direct contact cycle was discussed using FFT analysis, which is an important parameter in considering the heat transfer mechanism in MEB.